Remaining Recovery Period (years) Regulatory Liabilities, Remaining Recovery Period Regulatory Liabilities, Remaining Recovery Period Portion at Fair Value Measurement Portion at Fair Value Measurement [Member] UNS Electric Uns Electric [Member] UNS Electric . Guarantee, terms, no limitation to maximum potential future payment Guarantee, Terms, No Limitation to Maximum Potential Future Payment [true false] Short-term Debt, Type [Axis] Short-Term Debt, Type [Axis] Net Carrying Value Reported Value Measurement [Member] Subsequent Event Subsequent Event [Member] No Insider Trading Flag No Insider Trading Flag No Insider Trading Flag Document Fiscal Year Focus Document Fiscal Year Focus Derivative Instruments, Gain (Loss) by Hedging Relationship, by Income Statement Location, by Derivative Instrument Risk [Table] Derivative Instruments, Gain (Loss) [Table] Public utilities approved post test year plant additions Public Utilities Requested Post Test Year Plant Period Public Utilities Requested Post Test Year Plant Period Effective 1/1/2024-12/31/2026 Effective 1/1/2024-12/31/2026 [Member] Effective 1/1/2024-12/31/2026 Final mine reclamation liability Environmental Exit Costs, Costs Accrued to Date Common Stock (No Par Value, 75,000,000 Shares Authorized, 32,139,434 Shares Outstanding as of September 30, 2026 and December 31, 2025) Common Stock, Value, Issued Accrued Employee Expenses Employee-related Liabilities, Current Renewable Energy Credits Renewable Energy Credit Renewable Energy Credit Public Utilities, General Disclosures [Line Items] Public Utilities, General Disclosures [Line Items] EMPLOYEE BENEFITS PLANS Retirement Benefits [Text Block] Maximum exposure, undiscounted Guarantor Obligations, Maximum Exposure, Undiscounted Line of Credit Line of Credit [Member] Wholesale Wholesale Revenue [Member] Wholesale Revenue [Member] Expected Return on Plan Assets Defined Benefit Plan, Expected Return (Loss) on Plan Assets Derivative Instrument [Axis] Derivative Instrument [Axis] Battery storage Long-Term Purchase Commitment, Battery Storage Long-Term Purchase Commitment, Battery Storage Measurement Frequency [Axis] Measurement Frequency [Axis] Extension period Debt Instrument, Extension Period Debt Instrument, Extension Period Regulatory Liabilities Total Noncurrent Regulatory Liabilities Regulatory Liability, Noncurrent Income Taxes Paid (Refunds) Income Tax Paid, after Refund Received [Abstract] Amendment Flag Amendment Flag Current Liabilities Liabilities, Current [Abstract] Credit Loss Expense Accounts Receivable, Credit Loss Expense (Reversal) Schedule of Derivative Volumes Schedule of Notional Amounts of Outstanding Derivative Positions [Table Text Block] Energy efficiency implementation plan term Energy Efficiency Implementation Plan Term Energy Efficiency Implementation Plan Term Entity Common Stock, Shares Outstanding Entity Common Stock, Shares Outstanding Regulatory Assets [Roll Forward] Regulatory Assets [Roll Forward] Regulatory Assets [Roll Forward] Receivables Billing Status [Domain] Receivables Billing Status [Domain] PTC benefits Income Tax Expense (Benefit), Production Tax Credit Income Tax Expense (Benefit), Production Tax Credit Allowance For Equity Funds Allowance for Equity Funds Used During Construction Public Utilities, Allowance for Funds Used During Construction, Capitalized Cost of Equity Renewable Power Purchase Agreements Renewable Energy Power Purchase Agreement [Member] Renewable Energy Power Purchase Agreement [Member] Capital Stock Expense Capital Stock Expense [Member] Common stock expense. Approved recovery of spending budget Approved Recovery of Spending Budget Approved Recovery of Spending Budget Use of Renewable Energy Credits for Compliance Other Depreciation and Amortization Proposed earnings test deadband Annual Rate Adjustment Mechanism, Proposed Earnings Test Deadband Annual Rate Adjustment Mechanism, Proposed Earnings Test Deadband Commitments And Contingencies [Line Items] Commitments And Contingencies [Line Items] Commitments And Contingencies [Line Items] Amortization period Regulatory Asset, Amortization Period RELATED PARTY TRANSACTIONS Related Party Transactions Disclosure [Text Block] Schedule of Cash, Cash Equivalents Schedule of Cash and Cash Equivalents [Table Text Block] Entity Address, State or Province Entity Address, State or Province REGULATORY MATTERS Public Utilities Disclosure [Text Block] Assets Assets, Fair Value Disclosure [Abstract] Schedule of Regulatory Assets and Liabilities Schedule Of Regulatory Assets And Liabilities [Table Text Block] [Table Text Block] for Schedule of Regulatory Assets and Liabilities [Table] Retirement Benefits [Abstract] Retirement Benefits [Abstract] Schedule of Related Party Balances and Transactions Schedule of Related Party Transactions [Table Text Block] Fair Value, by Balance Sheet Grouping [Table] Fair Value, by Balance Sheet Grouping [Table] Total Capitalization Capitalization, Long-Term Debt and Equity Regulatory Assets Total Noncurrent Regulatory Assets Regulatory Asset, Noncurrent Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Collaborative Arrangement and Arrangement Other than Collaborative [Domain] Total Current Liabilities Liabilities, Current Regulatory Liability [Axis] Regulatory Liability [Axis] Taxes Other Than Income Taxes Taxes, Miscellaneous Derivative Instruments Derivative Liability, Current Short-term Debt, Type [Domain] Short-Term Debt, Type [Domain] Entity Address, City or Town Entity Address, City or Town Schedule of Cash and Non-Cash Transactions Schedule of Cash Flow, Supplemental Disclosures [Table Text Block] Components of Net Periodic Benefit Plan Cost Defined Benefit Plan Disclosure [Line Items] ACCOUNTS RECEIVABLE Loans, Notes, Trade and Other Receivables Disclosure [Text Block] Receivables [Abstract] Receivables [Abstract] Statement of Financial Position [Abstract] Statement of Financial Position [Abstract] Retail, Unbilled Unbilled Revenues [Member] Energy Efficiency Standards Energy Efficiency Standards [Member] Energy Efficiency Standards [Member] Basis of Presentation Basis of Accounting, Policy [Policy Text Block] Level 2 Fair Value, Inputs, Level 2 [Member] Receivable [Domain] Receivable [Domain] Other Income (Expense) Nonoperating Income (Expense) [Abstract] Line of credit facility borrowing capacity Line of Credit Facility, Maximum Borrowing Capacity Other Comprehensive Income (Loss), Net of Tax Other Comprehensive Income (Loss), Net of Tax Name of Property [Axis] Name of Property [Axis] 2026 Agreement 2026 Agreement [Member] 2026 Agreement Subsequent Event Type [Axis] Subsequent Event Type [Axis] Schedule of Long-term Debt Instruments [Table] Schedule of Long-Term Debt Instruments [Table] New Accounting Standards Issued, and Not Yet Adopted New Accounting Pronouncements, Policy [Policy Text Block] Fuel-Related Retail Revenues Fuel-Related Retail Revenues [Member] Fuel-Related Retail Revenues Tax credit percentage Investment Tax Credit, Additional Bonus Credit, Percent Investment Tax Credit, Additional Bonus Credit, Percent Related Party [Axis] Related and Nonrelated Parties [Axis] Schedule of PPFAC Regulatory Liability Balance Schedule of Regulatory Liabilities [Table Text Block] Guarantor Obligations [Line Items] Guarantor Obligations [Line Items] Document Period End Date Document Period End Date Changes in Current Assets and Current Liabilities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Increase (Decrease) in Operating Capital [Abstract] Net Cash Flows—Investing Activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation Cash Collateral Received/Posted Derivative Asset, Subject to Master Netting Arrangement, Collateral, Obligation to Return Cash Not Offset Preferred stock, shares outstanding (in shares) Preferred Stock, Shares Outstanding Total Regulatory Assets Regulatory Asset Accrued Capital Expenditures Construction in Progress Expenditures Incurred but Not yet Paid SUPPLEMENTAL CASH FLOW INFORMATION Cash Flow, Supplemental Disclosures [Text Block] Income Taxes Paid (Net of Refunds) Income Tax Paid, Federal, after Refund Received Total Liabilities Liabilities, Fair Value Disclosure Accumulated Other Comprehensive Loss Accumulated Other Comprehensive Income (Loss), Net of Tax Entity Shell Company Entity Shell Company Cash and Cash Equivalents [Line Items] Cash and Cash Equivalents [Line Items] Schedule of Allowance for Credit Losses Accounts Receivable, Allowance for Credit Loss [Table Text Block] Accrued Interest Interest Payable, Current Reportable Segments Segment Reporting, Policy [Policy Text Block] Gross, Net, and Offsetting Amounts [Line Items] Offsetting Liabilities [Line Items] Document Fiscal Period Focus Document Fiscal Period Focus Total Liabilities Liabilities Variable Interest Entities Consolidation, Variable Interest Entity, Policy [Policy Text Block] Corporate Services, UNS Energy UNS Energy to TEP [Member] UNS Energy to TEP [Member] Energy Derivative Contracts, No Regulatory Recovery Derivative Assets - No Regulatory Recovery Derivative Assets - No Regulatory Recovery Capital Expenditures Payments to Acquire Property, Plant, and Equipment Contributions from Parent Capital Contribution From Parent Capital Contribution From Parent Schedule of Restricted Cash Restrictions on Cash and Cash Equivalents [Table Text Block] Investment tax credit, maximum indemnities percentage Investment Tax Credit, Maximum Indemnification Percentage Investment Tax Credit, Maximum Indemnification Percentage Pension and Other Postretirement Benefits Expense Pension and Other Postretirement Benefits Cost (Reversal of Cost) Amortization of Debt Issuance Costs Amortization of Debt Issuance Costs and Discounts Operating Expenses Utilities Operating Expense [Abstract] Investment tax credits, amortization period Deferred Investment Tax Credits, Amortization Period Deferred Investment Tax Credits, Amortization Period Offsetting Liabilities [Table] Offsetting Liabilities [Table] Energy Derivative Contracts Energy Related Derivative [Member] Schedule of Regulatory Assets [Table] Regulated Operation, Regulatory Asset [Table] Investments and Other Property Other Long-Term Investments Average original cost of debt (percentage) Public Utilities, Requested Average Cost of Debt, Percentage Public Utilities, Requested Average Cost of Debt, Percentage Schedule of Financial Impact of Energy Contracts Derivatives Not Designated as Hedging Instruments [Table Text Block] Retail Billed Revenues [Member] Credit Facility [Domain] Credit Facility [Domain] Control Area Services, UNS Electric Tucson Electric Power Company To Uns Electric [Member] Tucson Electric Power Company To Uns Electric [Member] Related Party Transactions [Abstract] Related Party Transactions [Abstract] Cash Flows from Operating Activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation [Abstract] Accounts, Notes, Loans and Financing Receivable [Line Items] Accounts, Notes, Loans and Financing Receivable [Line Items] Disaggregation of Revenue [Line Items] Disaggregation of Revenue [Line Items] Capital Stock Expense Capital Stock Expense Capital Stock Expense Entity Emerging Growth Company Entity Emerging Growth Company Related Party Transaction [Line Items] Related Party Transaction [Line Items] Income Taxes Recoverable through Future Rates Income Taxes Payable through Future Rates Income Taxes Recoverable (Payable) through Future Rates Deferred Income Tax Charge [Member] Pension and Other Postretirement Benefits Liability, Defined Benefit Plan, Noncurrent Derivative Instruments Derivatives, Policy [Policy Text Block] Swingline Sublimit Swingline Line Of Credit [Member] Swingline Line Of Credit Deferred Income Taxes Deferred Income Taxes and Tax Credits Over-Recovered Fuel and Purchased Energy Costs Over Recovered Purchased Energy Costs [Member] Over Recovered Purchased Energy Costs Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Collaborative Arrangement and Arrangement Other than Collaborative [Axis] Regulatory Asset [Axis] Regulatory Asset [Axis] Current carrying value Guarantor Obligations, Current Carrying Value Gross Amount Recognized in the Balance Sheets Derivative Liability, Subject to Master Netting Arrangement, before Offset Revenue from Contract with Customer [Abstract] Revenue from Contract with Customer [Abstract] Restricted Cash Cash and Cash Equivalents, Restricted Cash and Cash Equivalents, Policy [Policy Text Block] Total Utility Plant, Net Public Utilities, Property, Plant and Equipment, Net Level 1 Fair Value, Inputs, Level 1 [Member] Roadrunner Reserve I Accounting Order Roadrunner Reserve I Accounting Order [Member] Roadrunner Reserve I Accounting Order Number of retail customers Entity Number Of Customers Entity number of customers. Derivative Instruments Derivative Asset, Noncurrent Organization, Consolidation and Presentation of Financial Statements [Abstract] Organization, Consolidation and Presentation of Financial Statements [Abstract] Massachusetts formula - TEP's allocation (percentage) Intercompany Allocation Parent To Subsidiary Intercompany Allocation Parent To Subsidiary Lost Fixed Cost Recovery Lost Fixed Cost Recovery Mechanism [Member] Lost Fixed Cost Recovery Mechanism [Member] Regulated Operations [Abstract] Regulated Operations [Abstract] Original cost rate base (percentage) Public Utilities, Requested Return On Rate Base, Percentage Public Utilities, Requested Return On Rate Base, Percentage Repayments of Borrowings, Revolving Credit Facility Repayments of Long-Term Lines of Credit Schedule of Components of Net Periodic Benefit Cost Schedule of Net Benefit Costs [Table Text Block] Depreciation Depreciation Expense Depreciation Number of extensions Debt Instrument, Number Of Extensions Debt Instrument, Number Of Extensions Guarantor Obligations, Nature [Axis] Guarantor Obligations, Nature [Axis] Fair Value Disclosures [Abstract] Fair Value Disclosures [Abstract] Debt Disclosure [Abstract] Debt Disclosure [Abstract] Debt Instrument, Name [Domain] Debt Instrument, Name [Domain] UNS Energy Uns Energy [Member] Uns Energy [Member] Borrowed Long-Term Line of Credit Arizona Corporation Commission Arizona Corporation Commission [Member] Arizona Corporation Commission [Member] Asset Retirement Obligations Increase (Decrease) Increase (Decrease) in Asset Retirement Obligations Schedule of Disaggregation of Revenue Disaggregation of Revenue [Table Text Block] Revenue from Contract with Customer Revenue from Contract with Customer1 [Member] Revenue from Contract with Customer1 Restricted Cash Restricted Cash and Cash Equivalent Counterparty Netting of Energy Contracts Derivative Asset, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Net Amount Derivative Asset, Subject to Master Netting Arrangement, after Offset and Deduction Public Utilities, Regulatory Proceeding [Domain] Public Utilities, Regulatory Proceeding [Domain] Derivatives (Note 9) Derivatives Derivative [Member] Non-fuel base rate increase (decrease) Public Utilities, Requested Rate Increase (Decrease), Amount Dividends Declared to Parent Dividends, Common Stock Net Periodic Benefit Cost Defined Benefit Plan, Net Periodic Benefit Cost (Credit) Gas Contracts BBtu Gas Contracts [Member] Gas Contracts [Member] Common stock, shares authorized (in shares) Common Stock, Shares Authorized Deferred Fuel and Purchased Power Costs Deferred Fuel And Purchased Power Costs Deferred Fuel And Purchased Power Costs Cash Flows from Investing Activities Cash Provided by (Used in) Investing Activity, Including Discontinued Operation [Abstract] Recurring Fair Value, Recurring [Member] Related Party Transaction [Axis] Related Party Transaction [Axis] Document Quarterly Report Document Quarterly Report Derivative Assets Derivative Asset [Abstract] Common Stock Common Stock Including Additional Paid in Capital [Member] Regulatory Liabilities Increase (Decrease) in Regulatory Liabilities DEBT AND CREDIT AGREEMENT Debt Disclosure [Text Block] Self-Insured Medical & Short-Term Disability Self-Insured Medical & Short-Term Disability [Member] Self-Insured Medical & Short-Term Disability Corporate Services, UNS Energy Affiliates UNS Energy Affiliates to TEP [Member] UNS Energy Affiliates to TEP [Member] Derivative Liabilities Derivative Liability [Abstract] Equity Component [Domain] Equity Component [Domain] Original cost rate base Public Utilities, Requested Original Cost Rate Base Public Utilities, Requested Original Cost Rate Base Performance Guarantee Performance Guarantee [Member] Accounts receivable, gross Accounts Receivables Accounts Receivable, before Allowance for Credit Loss, Current Counterparty Name [Domain] Counterparty Name [Domain] Total Common Stock Equity Beginning balance Ending balance Equity, Attributable to Parent Total Other Income (Expense) Nonoperating Income (Expense) Investment tax credit Investment Tax Credit ASSETS Assets [Abstract] Regulatory Agency [Axis] Regulatory Agency [Axis] Return on equity (percentage) Public Utilities, Requested Return on Equity, Percentage Regulatory Agency [Domain] Regulatory Agency [Domain] Other Other Operating Income Allowance for credit losses Retail, Allowance for Credit Losses Beginning of Period End of Period Accounts Receivable, Allowance for Credit Loss, Current Other, Net Proceeds from (Payment for) Other Financing Activity Derivative Instruments, Gain (Loss) [Line Items] Derivative Volume [Line Items] Derivative Instruments, Gain (Loss) [Line Items] Corporate services Selling, General and Administrative Expense Regulatory Assets Less Current Portion Regulatory Asset, Current Letter of Credit Letter of Credit [Member] COMMITMENTS AND CONTINGENCIES Commitments and Contingencies Disclosure [Text Block] Demand Side Management Demand Side Management [Member] Demand Side Management [Member] Number of operating segments Number of Operating Segments Common Stock, Shares Issued, Not Disclosed Common Stock, Shares Issued, Not Disclosed Common Stock, Shares Issued, Not Disclosed Entity Central Index Key Entity Central Index Key Commitments And Contingencies [Table] Commitments And Contingencies [Table] Commitments And Contingencies [Table] Regulatory Liabilities [Line Items] Regulatory Liability [Line Items] Accumulated Depreciation and Amortization Property, Plant, and Equipment, Accumulated Depreciation, Depletion, and Amortization Sales of Investment Tax Credits Proceeds from sale of investment tax credit Proceeds from sale of investment tax credit Proceeds From Sale Of Investment Tax Credit Proceeds From Sale Of Investment Tax Credit Name of Property [Domain] Name of Property [Domain] Other, Net Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity, Other Item Schedule of Guarantor Obligations [Table] Guarantor Obligation [Table] Net Cash Flows—Operating Activities Cash Provided by (Used in) Operating Activity, Including Discontinued Operation Renewable energy target percentage Renewable Energy Target Percentage Renewable Energy Target, Percentage Common Stock Equity: Equity, Attributable to Parent [Abstract] Income Statement [Abstract] Income Statement [Abstract] Document Transition Report Document Transition Report Fair Value Hierarchy and NAV [Axis] Fair Value Hierarchy and NAV [Axis] Other Other Receivable [Member] Other Receivable [Member] Sales of investment tax credits Investment Tax Credit Sold Investment Tax Credit Sold Basis of variable spread (in percentage) Debt Instrument, Basis Spread on Variable Rate City Area Code City Area Code Accumulated Other Comprehensive Loss AOCI Attributable to Parent [Member] Energy Derivative Contracts, Regulatory Recovery Derivative Liabilities - Regulatory Recovery Derivative Liabilities - Regulatory Recovery Long-Term Debt, including Current Maturities Debt Instrument, Fair Value Disclosure Transmission Revenues, UNS Electric Transmission Sales To UNS Electric [Member] Transmission Sales To UNS Electric [Member] Dividends Paid to Parent Payments of Dividends Pension and Other Postretirement Benefits (Note 8) Pension and Other Postretirement Plans Costs [Member] Regulatory Liability [Domain] Regulatory Liability [Domain] Statement [Line Items] Statement [Line Items] Total Assets Assets Derivative, energy measure Derivative, Nonmonetary Notional Amount, Energy Measure Net Periodic Benefit Plan Cost Components [Table] Defined Benefit Plan [Table] Retail Retail [Member] Power Contracts GWh Power Contracts [Member] Power Contracts [Member] Interest Expense Interest Expense, Nonoperating Total Assets (Liabilities), Net Fair Value, Net Asset (Liability) Long-term Purchase Commitment, Category of Item Purchased [Domain] Long-Term Purchase Commitment, Category of Item Purchased [Domain] Accrued Taxes Other than Income Taxes Accrual for Taxes Other than Income Taxes, Current Solar capacity Long-Term Purchase Commitment, Solar Capacity Long-Term Purchase Commitment, Solar Capacity Measurement Basis [Axis] Measurement Basis [Axis] Deferred Investment Tax Credits Deferred Investment Tax Credits [Member] Deferred Investment Tax Credits Other Noncurrent Liabilities Other Liabilities, Noncurrent Retirement Plan Type [Axis] Retirement Plan Type [Axis] Operations and maintenance expense, excluding customer funded expenses Operations And Maintenance Expense, Excluding Customer Funded Expenses Operations And Maintenance Expense, Excluding Customer Funded Expenses Counterparty Netting of Energy Contracts Derivative Liability, Subject to Master Netting Arrangement, Deduction of Financial Instrument Not Offset Cash Equivalents Cash Equivalents, at Carrying Value Subsequent Event Type [Domain] Subsequent Event Type [Domain] Retained Earnings Retained Earnings [Member] Total Operating Expenses Operating Expenses Revolver Revolving Credit Facility [Member] Allowance For Borrowed Funds Public Utilities, Allowance for Funds Used During Construction, Additions Fair Value Measurement Fair Value Measurement, Policy [Policy Text Block] Increase (Decrease) in Stockholder's Equity [Roll Forward] Increase (Decrease) in Stockholders' Equity [Roll Forward] Common stock, shares outstanding (in shares) Common Stock, Shares, Outstanding Roadrunner Reserve II Roadrunner Reserve II [Member] Roadrunner Reserve II Schedule of Face Value and Estimated Fair Value of Long-Term Debt Fair Value, by Balance Sheet Grouping [Table Text Block] Payment of Debt Issuance Costs Payments of Debt Issuance Costs Entity Current Reporting Status Entity Current Reporting Status Net Cash Flows—Financing Activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation Liabilities Liabilities, Fair Value Disclosure [Abstract] Unrealized Gains (Losses) on Investments Unrealized Gain (Loss) on Investments Proceeds from Borrowings, Revolving Credit Facility Proceeds from Long-Term Lines of Credit Adjustments to Reconcile Net Income to Net Cash Flows from Operating Activities: Adjustment to Reconcile Net Income to Cash Provided by (Used in) Operating Activity [Abstract] Write-offs Accounts Receivable, Allowance for Credit Loss, Writeoff Schedule of Potential Offset of Assets by Counterparty Netting and Cash Collateral Offsetting Assets [Table Text Block] 2021 Agreement 2021 Agreement [Member] 2021 Agreement Loss Contingency Nature [Axis] Loss Contingency Nature [Axis] Revenues from Contracts with Customers Revenue from Contract with Customer, Excluding Assessed Tax Cash Flows from Financing Activities Cash Provided by (Used in) Financing Activity, Including Discontinued Operation [Abstract] Additional collateral required to post if credit-risk contingent features are triggered Additional Collateral, Aggregate Fair Value Line of credit facility remaining borrowing capacity Line of Credit Facility, Remaining Borrowing Capacity Interest Cost Defined Benefit Plan, Interest Cost Regulatory Assets [Line Items] Regulatory Asset [Line Items] Non-Service Cost Defined Benefit Plan, Non-Service Cost [Abstract] Defined Benefit Plan, Non-Service Cost [Abstract] Net Cost of Removal Increase (Decrease) Net Cost Of Removal Of Interim Retirements Net cost of removal of interim retirements. Capacity Charges , UNS Gas UNS Gas to TEP [Member] UNS Gas to TEP [Member] Wholesale Revenues, UNS Electric Wholesale Revenues, UNS Electric [Member] Wholesale Revenues, UNS Electric Fair Value Estimate of Fair Value Measurement [Member] REVENUE Revenue from Contract with Customer [Text Block] Assets needed for immediate settlement, aggregate fair value Assets Needed for Immediate Settlement, Aggregate Fair Value Materials and Supplies Inventory, Raw Materials and Supplies, Net of Reserves Other Payment for (Proceeds from) Other Investing Activity Materials, Supplies, and Fuel Inventory Increase (Decrease) in Inventories PPFAC and Base Power Recoveries Purchased Power And Fuel Adjustment, Refunds (Recoveries) Purchased Power And Fuel Adjustment, Refunds (Recoveries) Schedule of Related Party Transactions, by Related Party [Table] Related Party Transaction [Table] Other Other Assets, Current Commitments and Contingencies Disclosure [Abstract] Commitments and Contingencies Disclosure [Abstract] Operating Income Operating Income (Loss) Current Fiscal Year End Date Current Fiscal Year End Date San Juan San Juan [Member] San Juan Amortization Amortization of Deferred Charges Related Party Transaction [Domain] Related Party Transaction [Domain] Entity File Number Entity File Number Service Cost Defined Benefit Plan, Service Cost Plant in Service Public Utilities, Property, Plant And Equipment, Generation, Transmission And Distribution Public Utilities, Property, Plant And Equipment, Generation, Transmission And Distribution Asset Retirement Obligations Asset Retirement Obligations, Noncurrent Equity Components [Axis] Equity Components [Axis] Other Services Other Services [Member] Other Services [Member] Accounts Receivable Increase (Decrease) in Accounts Receivable Related Party Related Party [Member] Product and Service [Domain] Product and Service [Domain] Unrealized Net Gain (Loss) Increase (Decrease) in Regulatory Assets and Liabilities Valuation allowance Deferred Tax Assets, Valuation Allowance Disaggregation of Revenue [Table] Disaggregation of Revenue [Table] Triggering Event [Domain] Triggering Event [Domain] Triggering Event Remaining Recovery Period (years) Remaining Recovery Period of Regulatory Assets for which No Return on Investment During Recovery Period is Provided Capitalization Capitalization, Long-Term Debt and Equity [Abstract] Entity Interactive Data Current Entity Interactive Data Current Deferred Income Taxes, Net Deferred Income Tax Liabilities, Net Contributions from Parent Proceeds from Contributions from Parent Entity Small Business Entity Small Business Restricted Cash included in: Restricted Cash [Abstract] Total Utility Plant Public Utilities, Property, Plant and Equipment, Plant in Service Fair Value, Recurring and Nonrecurring [Table] Fair Value, Recurring and Nonrecurring [Table] Other Other Liabilities, Current Other Noncurrent Assets Other Assets, Noncurrent Approved renewable energy standard increase in tariff amount Approved Renewable Energy Standard Increase In Tariff Amount Approved Renewable Energy Standard Increase In Tariff Amount Document Type Document Type Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] Derivative Instruments Derivative Asset, Current Wholesale Wholesale [Member] Wholesale [Member] Management fee Management Fee Management Fee Purchased power Operating Costs and Expenses Investment Tax Credits and Production Tax Credits Regulatory Income Taxes, Policy [Policy Text Block] Statement of Stockholders' Equity [Abstract] Statement of Stockholders' Equity [Abstract] Local Phone Number Local Phone Number Other Postretirement Benefits Other Postretirement Benefits Plan [Member] Purchased Power and Fuel Adjustment Clause Purchased Power and Fuel Adjustment Clause [Member] Purchased Power and Fuel Adjustment Clause [Member] Entity Address, Postal Zip Code Entity Address, Postal Zip Code Entity Registrant Name Entity Registrant Name NATURE OF OPERATIONS AND FINANCIAL STATEMENT PRESENTATION Organization, Consolidation, Basis of Presentation, Business Description and Accounting Policies [Text Block] Capital structure debt percentage Public Utilities, Requested Debt Capital Structure, Percentage Income Before Income Tax Expense Income (Loss) from Continuing Operations before Income Taxes, Noncontrolling Interest Commitments and Contingencies Commitments and Contingencies Operating Revenues Total Operating Revenues Revenues Triggering Event [Axis] Triggering Event [Axis] Triggering Event Accounts Payable and Accrued Charges Increase (Decrease) in Accounts Payable and Accrued Liabilities Renewable Energy Standard Renewable Energy Program [Member] Receivable Type [Axis] Receivable Type [Axis] Counterparty Name [Axis] Counterparty Name [Axis] CAPITALIZATION AND LIABILITIES Liabilities and Equity [Abstract] UNS Gas Uns Gas [Member] UNS gas. Schedule of Financial Instruments Measured at Fair Value on Recurring Basis Schedule of Fair Value, Assets and Liabilities Measured on Recurring Basis [Table Text Block] FV of derivative instruments in net liability position with credit risk related features, including normal purchase normal sale Derivative, Net Liability Position, Aggregate Fair Value Level 3 Fair Value, Inputs, Level 3 [Member] Months approved rate in effect unless modified Months Approved Rate In Effect Unless Modified Months approved rate in effect unless modified in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days. Supplemental Cash Flow Information [Abstract] Supplemental Cash Flow Information [Abstract] Restricted Cash Restricted Cash Billing Status, Type [Axis] Billing Status, Type [Axis] Retail Revenues Retail Revenues [Member] Retail Revenues Four Corners Four Corners [Member] Four Corners Credit Risk Concentration Risk, Credit Risk, Policy [Policy Text Block] Entity Tax Identification Number Entity Tax Identification Number Accounts Receivable, Allowance for Credit Loss [Roll Forward] Accounts Receivable, Allowance for Credit Loss [Roll Forward] Amortization Expense Amortization Excluding Amortization Of Debt Issuance And Discounts Amortization Excluding Amortization Of Debt Issuance And Discounts Approved spending budget Approved Spending Budget Approved Spending Budget Jointly Owned Utility Plant Interests [Line Items] Jointly Owned Utility Plant Interests [Line Items] Common Costs, UNS Energy Affiliates TEP to UNS Energy Affiliates [Member] TEP to UNS Energy Affiliates [Member] Capital structure equity percentage Public Utilities, Requested Equity Capital Structure, Percentage Cash, Cash Equivalents, and Restricted Cash, Beginning of Period Cash, Cash Equivalents, and Restricted Cash, End of Period Cash, Cash Equivalents, and Restricted Cash, End of Period Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Continuing Operation Cash Collateral Received/Posted Derivative Liability, Subject to Master Netting Arrangement, Collateral, Right to Reclaim Cash Not Offset Entity Incorporation, State or Country Code Entity Incorporation, State or Country Code Net Amount Derivative Liability, Subject to Master Netting Arrangement, after Offset and Deduction Capacity charges Related Party Transaction, Capacity Charges Related Party Transaction, Capacity Charges Measurement Frequency [Domain] Measurement Frequency [Domain] Debt Instrument [Axis] Debt Instrument [Axis] Public Utilities, Regulatory Proceeding [Axis] Public Utilities, Regulatory Proceeding [Axis] Allowance for Credit Losses Credit Loss, Financial Instrument [Policy Text Block] Customer Deposits Contract with Customer, Liability, Current Schedule of Regulatory Liabilities [Table] Regulated Operation, Regulatory Liability [Table] Total Current Assets Assets, Current Long-Term Debt, Net Long-Term Debt, Excluding Current Maturities Due from Affiliates (Note 5) Due From Affiliates [Member] Due From Affiliates [Member] Accounts Receivable (Net of Allowance for Credit Losses of $11,788 and $13,827 as of September 30, 2026 and December 31, 2025, respectively) Accounts Receivable, Net Accounts Receivable, after Allowance for Credit Loss, Current Purchased Power, UNS Electric Purchased Power, UNS Electric [Member] Purchased Power, UNS Electric Retained Earnings Retained Earnings (Accumulated Deficit) Product and Service [Axis] Product and Service [Axis] Pension Benefits Pension Plan [Member] Fair Value Measurement [Domain] Fair Value Measurement [Domain] Operating Leases Operating Lease, Cost Cover [Abstract] Cover [Abstract] Storage capacity Long-Term Purchase Commitment, Storage Capacity Long-Term Purchase Commitment, Storage Capacity Fuel and Purchased Power Fuel And Purchased Power Costs Fuel And Purchased Power Costs Fuel Inventory Energy Related Inventory Derivative Contract [Domain] Derivative Contract [Domain] Public Utilities General Disclosures [Table] Public Utilities General Disclosures [Table] Luna, Netting Luna, Netting [Member] Luna, Netting Total Capitalization and Liabilities Liabilities and Equity Derivative Instruments Derivative Liability, Noncurrent Regulatory Asset [Domain] Regulatory Asset [Domain] Interest Income Interest Income, Other Alternative Revenues Regulated Operating Revenue, Alternative Revenue Alternative Revenue Fair Value Inputs Assets Liabilities Quantitative Information [Line Items] Fair Value, Balance Sheet Grouping, Financial Statement Captions [Line Items] Construction Work in Progress Public Utilities, Property, Plant and Equipment, Construction Work in Progress Proceeds from Issuance, Long-Term Debt—Net of Discount Proceeds from Issuance of Senior Long-Term Debt Contributions in Aid of Construction Proceeds From (Refunds Of) Contribution In Aid Of Construction, Investing Activity Proceeds From (Refunds Of) Contribution In Aid Of Construction, Investing Activity Related Party [Domain] Related and Nonrelated Parties [Domain] Schedule of Accounts Receivable Schedule of Accounts, Notes, Loans and Financing Receivable [Table Text Block] Property Tax Deferrals Property Tax Deferrals [Member] Property Tax Deferrals [Member] Jointly Owned Utility Plant [Axis] Jointly Owned Utility Plant [Axis] Transmission Revenue Requirement Balancing Account Transmission Revenue Requirement Balancing Account [Member] Transmission Revenue Requirement Balancing Account Purchase Intangibles, Renewable Energy Credits Payments to Acquire Intangible Assets Other, Net Other Nonoperating Income (Expense) Operations and Maintenance Utilities Operating Expense, Maintenance, Operations, and Other Costs and Expenses FAIR VALUE MEASUREMENTS AND DERIVATIVE INSTRUMENTS Derivatives and Fair Value [Text Block] Preferred stock, shares authorized (in shares) Preferred Stock, Shares Authorized Total Regulatory Liabilities Regulatory Liability Jointly Owned Utility Plant [Domain] Jointly Owned Utility Plant [Domain] Preferred Stock (No Par Value, 1,000,000 Shares Authorized, None Outstanding as of September 30, 2026 and December 31, 2025) Preferred Stock, Value, Issued Percent of long-term trading contract gains shared with customers (percentage) Percent Of Gains Shared With Customers Percent Of Gains Shared With Customers Hedging Designation [Domain] Hedging Designation [Domain] Interest Paid, Net of Amounts Capitalized Interest Paid, Excluding Capitalized Interest, Operating Activity Statement of Cash Flows [Abstract] Statement of Cash Flows [Abstract] Utility Plant Public Utilities, Property, Plant and Equipment [Abstract] Pension and Other Postretirement Benefits Funding Payment for Pension and Other Postretirement Benefits Hedging Designation [Axis] Hedging Designation [Axis] Trade Accounts Trade Accounts Receivable [Member] Credit Facility [Axis] Credit Facility [Axis] Total Assets Assets, Fair Value Disclosure Early Generation Retirement Costs Early Generation and Retirement Costs [Member] Early Generation and Retirement Costs Schedule of Cash and Cash Equivalents [Table] Cash and Cash Equivalent [Table] Accounts Payable Accounts Payable, Current Fair Value Hierarchy and NAV [Domain] Fair Value Hierarchy and NAV [Domain] Debt Instrument [Line Items] Debt Instrument [Line Items] Other Current Assets Increase (Decrease) in Other Current Assets Retirement Plan Type [Domain] Retirement Plan Type [Domain] Entity Filer Category Entity Filer Category Guarantor Obligations, Nature [Domain] Guarantor Obligations, Nature [Domain] Other Regulatory Assets Other Regulatory Liabilities Other Regulatory Assets (Liabilities) [Member] Schedule of Potential Offset of Liabilities by Counterparty Netting and Cash Collateral Offsetting Liabilities [Table Text Block] Schedule of PPFAC Regulatory Asset Balance Schedule of Regulatory Assets [Table Text Block] Net Cost of Removal Removal Costs [Member] Cash and Cash Equivalents Cash and Cash Equivalents Cash and Cash Equivalent Investment tax credit, maximum indemnification, limitations period Investment Tax Credit, Maximum Indemnification, Limitations Period Investment Tax Credit, Maximum Indemnification, Limitations Period Beginning of Period End of Period Net Regulatory Assets Not Designated as Hedging Instrument Not Designated as Hedging Instrument [Member] Schedule of Accounts, Notes, Loans and Financing Receivable [Table] Accounts and Financing Receivables [Table] Cap on increase in lost fixed cost recovery rate (percentage) Cap On Increase In Lost Fixed Cost Recovery Rate Year over year cap on Increase in Lost Fixed Cost Recovery rate. Current Assets Assets, Current [Abstract] Reduction in Service Fees Reduction In Service Fees [Member] Reduction In Service Fees Entity Address, Address Line One Entity Address, Address Line One Non-Fuel Retail Revenues Non-Fuel Retail Revenues [Member] Non-Fuel Retail Revenues Income Tax Expense Income Tax Expense (Benefit) Jointly Owned Utility Plant Interests [Table] Regulated Operation, Jointly Owned Utility Plant [Table] Regulatory Assets Increase (Decrease) in Other Regulatory Assets Loss Contingency, Nature [Domain] Loss Contingency, Nature [Domain] Net Increase (Decrease) in Cash, Cash Equivalents, and Restricted Cash Cash, Cash Equivalent, Restricted Cash, and Restricted Cash Equivalent, Period Increase (Decrease), Including Exchange Rate Effect and Discontinued Operation Transportation Electrification and Electric Vehicle Infrastructure Transportation Electrification and Electric Vehicle Infrastructure [Member] Transportation Electrification and Electric Vehicle Infrastructure Accumulated deferred investment tax credit Deferred Tax Assets, Net of Valuation Allowance Energy Derivative Contracts, Regulatory Recovery Derivative Asset - Regulatory Recovery Derivative Asset - Regulatory Recovery Amortization of Net Loss Defined Benefit Plan, Amortization of Gain (Loss) Net Income Net Income Net Income Net Income (Loss) Attributable to Parent Balance Sheet Location [Axis] Location, Statement of Financial Position, Balance [Axis] Statement [Table] Statement [Table] Regulatory Liabilities Less Current Portion Regulatory Liability, Current Tax Credit Transfer Indemnification Tax Credit Transfer Indemnification [Member] Tax Credit Transfer Indemnification Area in which company generates transmits and distributes electricity to retail electric customers (sq miles) Area In Which Subsidiary Generates Transmits And Distributes Electricity To Retail Electric Customers Area in which subsidiary generates transmits and distributes electricity to retail electric customers. Gross Amount Recognized in the Balance Sheets Derivative Asset, Subject to Master Netting Arrangement, before Offset Number of claims Loss Contingency, New Claims Filed, Number Roadrunner Reserve I Roadrunner Reserve I [Member] Roadrunner Reserve I Common costs Common Costs Charged Common Costs Charged - Common Cost Allocations Collateral posted Collateral Already Posted, Aggregate Fair Value Category of Item Purchased [Axis] Category of Item Purchased [Axis]